Creating an Ideal Microclimate: HVAC Considerations for Greenhouses

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ideal greenhouse microclimate

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A greenhouse is an ideal choice of backyard structure for those who want to grow a range of plants in ideal conditions. They’re also used by many businesses to grow plants at large scale, providing the best chances of plant survival and high yields. 

However, to produce optimal results, greenhouses require appropriate HVAC systems. This guide will explain more.

Key Factors Affecting Greenhouse Climate

what affects a greenhouse climate

The microclimate inside a greenhouse is very different from the climate outside. Temperatures are typically higher inside these structures, while humidity levels are also more intense. 

However, even the best greenhouses can be affected greatly by the weather conditions around them, including:

  • Temperature – It’s usually warmer inside a greenhouse than out of it due to the way in which the glass works to magnify and intensify the sun’s heat passing through. However, if it’s cold and frosty outside a greenhouse, it’ll also be quite cold on the inside, as these houses don’t tend to have much insulation.
  • Humidity – Surrounding humidity levels can also impact the conditions inside a greenhouse. If the outside air is very dry, with low humidity levels, building up moisture and humidity inside may be more challenging. Similarly, if the outdoor air is wet and humid, causing common lawn problems outside the greenhouse, it may also lead to hotter and stickier air inside it.
  • Ventilation – The type and amount of ventilation in a greenhouse’s design will also impact its climate in a big way. Fans and vents allow fresh air to pass into the greenhouse while promoting good airflow throughout the space. This directly affects the temperature and humidity, and airflow is also needed to deal with any pests that could plague your plants.

It’s clear that these conditions need to be carefully controlled and optimized in order to encourage ideal plant growth. Many of the plant species grown in greenhouses may be sensitive and require specific temperatures and humidity levels to prosper. If the microclimate isn’t quite right, such plants will struggle to survive.

Ways to Heat a Greenhouse

As well as considering the design, layout, types of drainage, and other key aspects of your greenhouse, you need to think about how you’re going to heat it up and maintain a steady, constant interior temperature. There are multiple methods you can use to do this:

  • Hot water heating systems – Hot water heating is one of the most traditional heating options for greenhouses. In fact, this kind of system was used way back in the 19th century. It involves hot water pipes being installed under the greenhouse beds. Hot water can then be fed through the pipes, warming the greenhouse from below.
  • Unit heaters – Unit heaters are very powerful space heaters that can be installed to provide heat for the entire greenhouse. A good advantage of unit heaters is that they can save space when compared to other heating systems, but they require a lot of power to function, especially in big greenhouses.
  • Radiant heatersRadiant heaters are another option. They function by radiating heat around the greenhouse and can help to increase the temperature throughout the space. The downside with these heaters is that they may produce very hot spots in certain areas and cooler spots further away from the heaters themselves.
  • Electric heating mats – Finally, electric heating mats can be installed underground beneath the greenhouse or, at floor level, beneath the soil beds. These heaters work similarly to hot water systems, producing heat that radiates slowly upwards from the ground.

Ways to Cool and Ventilate Your Greenhouse

heating and cooling a greenhouse

There is also a wide range of cooling and ventilation systems that can be used to keep greenhouses cool and fresh:

  • Natural ventilation – A budget-friendly option is to rely on natural ventilation. Vents and openings can be fitted around the greenhouse to simply let the natural breeze pass through, blowing fresh, clean air into the greenhouse and aiding with circulation. The downside with this is that pests can also enter this way, and it won’t work well on calm days.
  • Exhaust fans – Exhaust fans are one of the most common methods of greenhouse ventilation. They’re usually positioned in the end wall of the greenhouse and pull air through the greenhouse with the aid of strong motors.
  • Circulating fans – Another option is to install circulating fans. As the name implies, these fans are designed to aid with the circulation of air around the greenhouse, keeping it flowing at all times to promote a steady temperature. 
  • Thermostat – A thermostat system can also be fitted inside a greenhouse to directly sense and control the temperature as it changes throughout the days and nights. The thermostat can detect the temperature at any time and then trigger fans or heating systems to switch on and off accordingly. 

Future Trends and Advancements in Greenhouse HVAC Technology

As technology continues to advance, the greenhouse industry is poised to witness significant innovations and adaptations in HVAC systems to ensure improved temperature and climate control. 

This trend is particularly relevant in regions experiencing prolonged periods of hot and dry weather. A key focus in this field is the development of sustainable and eco-friendly solutions. 

Heating and air conditioning companies are actively working on greenhouse fans and climate control systems that prioritize energy efficiency while delivering the desired high-performance levels demanded by greenhouse owners.


Overall, greenhouses can’t simply do all the work on their own. The glass, frame, and structure help to provide the basic foundations of a microclimate, but additional ventilation and HVAC systems are needed to control the temperature, humidity levels, and more truly. Any individual or business wanting to get the best value out of a greenhouse needs to consider an investment in the appropriate HVAC technology.

  • Mark Miller

    Mark Miller, a skilled technical writer and HVAC expert with over 5 years of industry experience, is currently working with The Cooling Company. With his extensive knowledge of heating, ventilation, and air conditioning systems, Mark is passionate about creating informative content for both homeowners and industry professionals. He takes pride in his work and strives to share his expertise in a way that is easy to understand and helpful to his readers. Mark enjoys hiking and spending time with his family when he's not writing.

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